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A series of Streptococcus pyogenes strains, including strains isolated from patients, mutants which had acquired in vitro resistance to penicillin (Pc), mitomycin C (MC), tetracycline (TC) and chloramphenicol (CM), ultraviolet light induced α hemolytic mutants, as well as β hemolytic mutants (β mutants) derived from α hemolytic mutants (α mutants) were compared as to their antibiotic sensitivity, and physiological, biochemical and serological properties. To obtain β mutants from α mutants the following procedures were employed: (1) serial mouse passage, (2) serial serum‐broth transfers, (3) cultivation in heat‐killed cultures of parent strains, and (4) cultivation in broth containing bacterial DNA extracted from parent streptococcus cells. From the results obtained these strains could be divided into two major groups, each with two subgroups. Group 1 strains produce soluble hemolysins and are sensitive to Pc. Subgroup 1–1 strains are sensitive to other antibiotics too; subgroup 1–2 are resistant to certain antibiotics other than Pc, bacitracin and MC. Group 2 strains do not produce soluble hemolysins and resistant to Pc. Subgroup 2‐1 strains are α hemolytic on horse blood agar and subgroup 2–2 are β hemolytic on the same medium. Pc resistance in group 2 strains was more than 100‐fold higher than that of sensitive strains, and was accompanied by MC resistance, but to a lesser degree. Pc resistance in group 2 mutants could be induced by antibiotics other than Pc and also by ultraviolet irradiation. Although group 1 cells retained the characteristics of typical S. pyogenes, group 2 cells, both α and β hemolytic, lost most of the physiological, biochemical and serological properties of this species. The similarity of group 2 strains to group D or group N streptococcal strains in their general properties is discussed.
A series of Streptococcus pyogenes strains, including strains isolated from patients, mutants which had acquired in vitro resistance to penicillin (Pc), mitomycin C (MC), tetracycline (TC) and chloramphenicol (CM), ultraviolet light induced α hemolytic mutants, as well as β hemolytic mutants (β mutants) derived from α hemolytic mutants (α mutants) were compared as to their antibiotic sensitivity, and physiological, biochemical and serological properties. To obtain β mutants from α mutants the following procedures were employed: (1) serial mouse passage, (2) serial serum‐broth transfers, (3) cultivation in heat‐killed cultures of parent strains, and (4) cultivation in broth containing bacterial DNA extracted from parent streptococcus cells. From the results obtained these strains could be divided into two major groups, each with two subgroups. Group 1 strains produce soluble hemolysins and are sensitive to Pc. Subgroup 1–1 strains are sensitive to other antibiotics too; subgroup 1–2 are resistant to certain antibiotics other than Pc, bacitracin and MC. Group 2 strains do not produce soluble hemolysins and resistant to Pc. Subgroup 2‐1 strains are α hemolytic on horse blood agar and subgroup 2–2 are β hemolytic on the same medium. Pc resistance in group 2 strains was more than 100‐fold higher than that of sensitive strains, and was accompanied by MC resistance, but to a lesser degree. Pc resistance in group 2 mutants could be induced by antibiotics other than Pc and also by ultraviolet irradiation. Although group 1 cells retained the characteristics of typical S. pyogenes, group 2 cells, both α and β hemolytic, lost most of the physiological, biochemical and serological properties of this species. The similarity of group 2 strains to group D or group N streptococcal strains in their general properties is discussed.
Group A streptococcus mutants, which lost the ability to produce soluble hemolysins, either β or α hemolytic on the horse blood agar, showed penicillin‐mitomycin C double resistance. Penicillin resistance was high and stable, but mitomycin C resistance was not remarkably high. Mitomycin C resistance was always accompanied with inactivation of the antibacterial activity of the drug, while mitomycin C and penicillin sensitive group A streptococci never showed mitomycin inactivation. The component affecting the mitomycin C was not found in the sterile filtrate of mutant cell cultures, nor could it be extracted by sonic oscillation. The activity of the factor diminished, when living mutant cells were heated at 60 C for 30 min, but activity was not diminished at 56 C. The intensity of activity was a function of the bacterial quantities used. Mutant cells suspended in heart infusion broth, proteose peptone, casamino acid and horse serum were able to render the factor which inactivated mitomycin C, while mutant cells suspended in bovine serum albumin, RNA, or saline did not show the phenomenon.
Transfers of Streptococcus pyogenes strain T12 in Todd–Hewitt broth containing stepwise increases in amounts of mitomycin C (MC) gave rise to slight changes of their colonial appearances. Variants thus obtained were examined for antibiotic and bile resistances; production of streptolysin‐S, ‐O and deoxyribonuclease; growth in alkaline medium, high salt concentration, and at 10 C and 45 C; sugar fermentations, and precipitin reactions. Four strains retained group A antigen, but some of them lost the ability to produce hemolysins and deoxyribonuclease, and acquired resistance to bile, penicillin and streptomycin as well as MC, and to physical environments. Four other strains lost group A antigen and acquired new antigens common to cells of group C, group D, or highly antibiotic‐resistant mutants reported previously. A variant which reacted with group C antiserum contained galactosamine, but not glucosamine, while the parent strain showed the reverse pattern. Many other variants contained both hexosamines. Even a variant, strain TL3‐2, reacted strongly only with group A antiserum, but contained glucose and both hexosamines. These strains having galactosamine possessed uridine diphosphate (UDP)‐N‐acetylglucosamine‐4‐epimerase activity which converted the substrate into UDP‐N‐acetylgalactosamine, while the parent strain failed to demonstrate the existence of this enzyme. The variants were discussed with respect to the group A streptococcal variations possessing no more original characteristics.
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